Circuit arrangement in an electronic watch employing a balance



July 22, 1969 A. NOGAREDE CLF-CCH AMAN-immer m AN ELECTRONIC WATCH EMFLOYINC A BALANCK Filed April 18, 1967 2 Sheets-Sheet l July A22, 1969 A. NOGAREDE 3,456,436

CIRCUIT ARRANGEMEII'E IN AN ELECTRONIC WATCH IZMFLOYING A EALANCE Filed April 18, 1967 2 Sheets-Sheet E United States Patent O 3,456,436 CIRCUIT ARRANGEMENT IN AN ELECTRONIC WATCH EMPLOYING `A BALANCE Adrien Nogarede, Communal 2, Le Locle, Switzerland Continuation-impart of application Ser. No. 390,404, Aug. 18, 1964. This application Apr. 18, 1967, Ser. No. 631,787

Int. Cl. G04c 3/04 U.S. Cl. 58--28 5 Claims ABSTRACT OF THE DISCLOSURE In combination with an electronic watch wherein the balance stafr carries an oscillating permanent magnet, the oscillations of which induce impulses in a control winding which impulses are returned to the magnet through a driving winding after ampliication, a rst circuit, a source of electrical energy including positive and negative terminals feeding energy in the circuit, a first transistor inserted through its emitter and collector in the circuit between the terminals, a `iirst resistance between the emitter of the transistor have a corresponding terminal, a second circuit connecting the emitter of the transistor with the negative terminal connected with the collector of the transistor, a further resistance inserted in the second circuit, a shunt circuit connecting a point of the second circuit located between the emitter of the transistor and the further resistance with the base of the transistor, a watch control winding in the shunt circuit, a condenser inserted in the second circuit between the emitter of the first transistor and the further resistance, the charging of the condenser producing during transient oscillatory periods of the `watch on the base of the iirst transistor a potential such as will make the latter operate as a Class A amplier; a third circuit set across the terminals in parallel with the first transistor and the first resistance, a second transistor in series with the first transistor to provide the amplification, a second upkeep winding between a collector of the second transistor and the corresponding negative terminal, means connecting directly the base of the second transistor with the emitter of the iirst transistor, the rating of the further resistance being such that during lthe transient oscillatory periods of the watch, the second transistor operates as a Class A amplifier, the two transistors operating as Class B amplitiers during the normal operative periods of the Watch as soon as the first mentioned condenser has lost the major part of its load and is at a voltage lower than the threshold voltage of the first transistor.

This application is a continuation-in-part of my previous application Ser. No. 390,404 filed Aug. 18, 1964 now abandoned.

In U.S. Patent 3,124,731 issued on Mar. 10, 1964, to Richard Eysen and to the applicant herein, it has already been proposed to produce an electronic watch wherein the balance staff carries a permanent magnet, the oscillations of which induce pulses in a control Winding, which pulses are returned back to the magnet through a driving or upkeep winding after amplification by at least one transistor.

In said patent, the axis of the magnet lies for the inoperative position of said magnet at a distance from the common axis of the two windings which is transiently coaxial for each half alternation, said distance being such that the magnet has a tendency to stop in the area subjected to the action of the winding, while a potential is applied to the base of at least one transistor at least at the moment of the starting in a manner such that a cur- ACe rent is produced between the emitter and the collector, which is larger than the current of the transistor under inoperative conditions, said current being adapted to flow through the driving winding and to initiate the oscillations of the balance wheel.

In order to remove the drawbacks appearing when starting such a mechanical oscillator, circuits have been proposed which include one or two transistors through which a voltage is applied, under the control of a manual switch, or else, of a voltage divider incorporated with the circuit, to the base of at least one transistor in a manner such that the inoperative current passing through the upkeep winding increases until it reaches a value such that it is capable, for transient conditions, to start the oscillatory movement of the balance wheel and to bring it into permanent operative conditions for which the amplitude of oscillation remains at a constant value.

The first solution proposed has the drawback of requiring the intervention of an operator for each start of the watch, lwhereas the second solution does not furnish a suhcient biasing voltage to use silicon transistors of which the great thermic stability and lower cost makes them preferable to the standard germanium transistors.

The present invention has for its object an electronic watch of the type claimed in said |U,S. patent.

According to the present invention and as illustrated in the accompanying FIGURE l, a first transistor has its emitter connected with one of the poles of the battery through a resistance 2, while in the base emitter circuit of said transistor there is inserted a control winding 12 and a condenser 4 which is loaded through said resistance 2 and a further resistance 1 by the supply of current. The loading voltage produced by the mechanical oscillations of the system during its transient operative conditions applies on the base of the transistor T1 a potential such that the latter operates as a Class A amplifier. In the collector circuit of a second transistor T2 is inserted the upkeep winding 13 while its emitter-base circuit includes the resistance 2, the base of said transistor T2 being connected with the emitter of the transistor T1, said transistor T2 operating during the transient oscillating conditions of the mechanical system under class A conditions also. In contradistinction, during the oscillations under permanent conditions, the two transistors T1 and T2 operate as Class B amplifiers, since the condenser 4- which has lost a large fraction of its load remains at a voltage lower than the threshold voltage of the transistor T1.

The accompanying drawings illustrate, by way of example, an embodiment of the present invention.

In said drawings:

FIGURES l and 2 are two wiring diagrams corresponding to said invention.

The circuit according to FIGURE 1 includes as already mentioned a supply of current S, a control winding 12, an upkeep winding 13 and two transistors T2 and T1; the base emitter circuit of the transistor T1 includes the control winding 12 and a condenser 4 lwhich is loaded through the resistances 1 and 2. The condenser 5 is inserted between the base and the collector of the transistor 1. A resistance 3 is inserted in the feed circuit.

The transistor T2 includes in its base-emitter circuit the above-mentioned resistance 2 and in its collectoremitter circuit the control winding 13 and the supply of current S.

The base of the transistor T1 is connected with the negative pole of the battery through the agency of the control winding 12 and of the resistance 1. The rating of the latter is such that, in the absence of any oscillation and during transient operation, said transistor operates as a Class A amplier.

The transistor T2 the base of which is connected directly with the emitter is adapted to operate Ialso as a Class A amplifier in the absence of any mechanical oscillations of the system or during transient operation as a consequence of a suitable value given to the resistance 2. The driving or upkeep winding B2 is inserted in series in the circuit of the collector of the second transistor T2.

Since the amplifier system operates as a Class A amplifier, its gain is very high, even for extremely weak signals. Said gain is sufficient for the least fluctuation of the current in the upkeep winding to produce small movements of the balance wheel as in initiation of the starting of the oscillations of the spiral spring and balance wheel system. The variations of the current produced by the background noises in the transistor are, for instance, suicient for initiating the mechanical oscillatory movement.

On the other hand, the least movement of the balance wheel induces a small electromotive force in the control winding, which, after amplification, starts the mechanical oscillations. The small shifting of the balance wheel produced by the establishment of the inoperative current defining operation as a Class A amplifier is sufficient for starting such oscillations.

The two phenomena referred to make it possible to reliably obtain under any conditions whatever the selfstarting of the oscillations of the spiral spring and balance wheel system.

Upon energization of the circuit, the condenser 4 is loaded through the resistances 1 and 2. Its loading voltage is stabilized transiently at a value which is slightly larger than the threshold voltage across the base and emitter of the transistor T1 which starts this operation under Class A conditions.

From this moment onwards, the balance wheel 14 begins oscillating. As the amplitude of mechanical oscillations increases, the electromotive force induced in the control winding 12 increases also proportionally to the speed of the magnet 11 and consequently the control current in the emitter base circuit of the transistor T1 also increases.

Said current passes also through the condenser 4 in a direction such that for each current pulse the condenser loses a fraction of its load. If the resistances 1 and 2 are correctly rated, the voltage across the terminals of the condenser 4 drops gradually down to a value lower than the threshold voltage across the base Iand emitter of T1 which operates now as a Class B amplifier or even as a Class C amplifier.

The transistor T1 requires thus practically no current between the successive pulses.

During the interval between two successive pulses, the current reloading the condenser 4 remains very low by reason of the large value given to the resistance 1; there is obtained across the terminals of the resistance 2 a drop in voltage which is much lower than the threshold voltage between the base and the emitter in the transistor T2, which latter operates now as. a Class B amplifier.

In order that the amplitude of oscillation of the balance wheel 14 during permanent operative conditions may be independent of any dispersion of the properties of the transistor and in particular of the gain of current, it is sufiicient that during the driving pulse the transistor T2 may be saturated. As a matter of fact, in such a case the current pulse in the upkeep winding 13 is limited to a practically constant value by the ohmic resistance of said winding.

Similarly, the resistance 3 inserted between the collector of T1 and the negativepole of the battery allows limiting the current in the emitter circuit of said transistor to the value required for a reliable and accurate operation of the transistor T2.

This allows reducing substantially the consumption of current bythe amplifier.

The condenser 5 inserted between the collector Iand the base of the transistor T1 ensures the cutting out of the high frequency electric oscillations produced by the direct magnetic coupling between the control and upkeep windings.

The direct connection between the resistance 1 and the transistor collector T2 produces a negative reaction which ensures a stabilization of the inoperative transistor current under the conditions of Class A. As a matter of fact, if the inoperative current T2 is too high, the voltage of its collector drops and consequently the biasing of T2 also drops. The reverse phenomenon is obtained.

The variable resistance 6 inserted in series with the upkeep Winding allows adjusting the amplitude of the oscillations of the balance wheel and spiral spring system.

The leak current from the alloyed or diffused silicon transistors which is extremely low remains negligible with reference to their operative current within a range of temperatures rising up to very high temperatures. Because of the high leakage currents of germanium transistors over 40 C. it is advantageous that the present device avoids their use. Another advantage of the present device is that it is much cheaper to use in series two silicon transistors rated at 20 thereby giving an amplifying coefiicient of 400 than to use a single transistor rated at 300 or 400.

What is claimed is:

1. In an electronic watch a balance staff carrying a coil support on each of its ends a balance wheel mounted on said staff located between said coil supports, an oscillating permanent magnet, the oscillations of which induce impulses in a control winding, which impulses are returned to said magnet through a driving winding after amplification; a first circuit, including a source of electrical energy having positive and negative terminals feeding energy into said circuit, a -rst transistor having a predetermined threshold voltage inserted through its emitter and collector in said circuit between said terminals, a first resistance inserted between the emitter of the said transistor and the corresponding terminal, a second circuit'connecting the emitter of said transistor with the negative terminal connected with the collector of said transistor, a further resistance inserted in said second circuit, a shunt circuit connecting a point of said second circuit located between the emitter of said transistor and said further resistance with the base of said transistor, a watch control winding in said shunt circuit located above said permanent magnet and mounted on one of said coil supports, a condenser inserted in said second circuit between the emitter of the first transistor and said further resistance, the charging of the condenser producing during the transient oscillatory periods of the watch on the base' of the first transistor, a potential such as will make the latter operate as a Class A amplifier, a third circuit fed across said terminals in parallel with said transistor and first resistance, a second transistor in series with said first transistor to provide said amplification, a second upkeep winding mounted on the other end of said coil supports and below said permanent magnet and inserted between the collector of the second transistor and the corresponding negative terminal, means connecting directly the base .of the second transistor with the emitter of the first transistor, the rating of the further resistance being such thatduring the transient oscillatory periods of the watch, said second transistor operates as a Class A amplifier, the twotransistors operating as Class B amplifiers during the normal operative periods of the watch as soon as the firstmentioned condenser has lost the major part of its load and is at a voltage lower than said threshold voltage of the first transistor.

2. The combination according to claim 1, having an auxiliary condenser between said base and said collector therefor of said rst transistor to damp high frequency oscillations.

3. The combination according to claim 1, wherein said 4. The combination according to claim 3, having a 5 variable resistance in said third circuit between the co1- lector of said second transistor and said second upkeep coil.

5. The combination according to claim 1, having an auxiliary resistance between the collector 0f said rst transistor and said negative terminal whereby to limit the current in sail collector,

6 References Cited UNITED STATES PATENTS 2,814,769 11/1957 Williams 58-23 3,046,460 7/1962 Zemla 58-23 OTHER REFERENCES Harry Diamond Laboratories-Induction-Triggered Two- Terminal Electronic Clock Driver, Feb. 29, 1964, No. 1.

ROBERT S. WARD, IR., Primary Examiner EDITH C. SIMMONS, Assistant Examiner 

